Eyes half shut?

Offices throughout the capital may soon have a spy that can tell whether employees have drunk alcohol, taken drugs - or even had a late night.

An optical detection kit, costing £10,000 and unveiled to business leaders today, gives an instant reading that shows whether a person is "under the influence" or fatigued. But it has ignited controversy among civil rights groups over infringement of employees' privacy.

The device, which looks like a pair of binoculars and is attached to a computer, works by flashing a green light into the pupil three times and measuring the speed of the pupil's contraction and dilation to decide whether a person is impaired by drugs or alcohol.

Another test works to establish whether a person is severely tired.

Chris Wakeham from Hampton Knight, the device's British distributor, said: "It can't yet differentiate between alcohol and drugs but employers can then carry out secondary tests such as mouth swabs or breath tests to work out which drug is involved."

The launch is the latest development in the effort to stop the mounting problem of substance abuse, and follows the revelation last week that binge drinking costs the UK economy £20 billion a year in accidents and days off work. The All-Party Parliamentary Group has been charged with looking into drugs and alcohol in advance of a new Government strategy early next year.

Unlike other methods, the new kit reveals whether a person is under the influence of drink or drugs at the time of testing.

Consultant Jamie Deas said the new method would be attractive to employers as a replacement for old methods, which were largely "ineffective and expensive."

He said: "The problem with conventional tests like the urine test is that they detect drugs that have been in the body for anything up to three or four weeks. That obviously is no good when you are attempting to find out if someone is directly under the influence of a drug like cannabis."

But Mark Littlewood, campaigns director at Liberty, said: "We think testing your workers for drugs or alcohol is unnecessary and intrusive. If their professional performance is inadequate then they can be subjected to normal disciplinary procedures."

It was revealed this summer that drunkenness and drug-taking is rife among London Underground employees, while the Government announced it may introduce random drug tests for police officers in England and Wales.